1. Field of the invention
This invention relates in general to helicopter drive trains, and in particular to a means for disengaging one engine in a twin engine helicopter from the blade drive train so that it will drive accessories while the other engine is off.
2. Description of the Prior Art
In a twin engine helicopter, both engines connect to a blade drive train for driving the blades and the tail rotor. An accessory gear will be connected into the drive system at one point for driving accessories such as hydraulic pumps, air conditioner pumps, generators and the like. During normal flight, the accessory gear will be rotating along with the blade and tail rotor.
There are times when for reasons such as maintenance, an operator would want to run the accessories with one engine without rotating the blade or tail rotor. In one prior art type, this is handled by a disengaging mechanism which disengages one engine from the blade drive train. This disengaging system requires that both engines be turned off before reengaging the engines with the blade drive train.
Consequently, after operating one engine to run the accessories, the operator would have to turn that engine off, then restart both engines with the blade train engaged. As the engines are normally started with battery power, this can be a problem. Considerable energy is required to start an engine from the battery. It may be difficult at times to restart the engines.
In another prior art type, the blade train can be re-engaged while one of the engines is running. As far as is known, this system removes an inner race from one of the input overrunning clutches during disengagement, and re-inserts the inner race to reengage. The input overrunning clutches are safety clutches that enable a helicopter to land with blade rotation in the event of engine failure. The input clutches will also allow one engine to drive the helicopter blade without the other engine. While workable, problems may occur as a result of removal and insertion of an inner race of an overrunning clutch.